Date: Fri, 15 Aug 2003 14:16:14 -0700
From: Andrew Morton <akpm@osdl.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [BUG] slab debug vs. L1 alignement
Message-Id: <20030815141614.29fc6768.akpm@osdl.org>
In-Reply-To: <1060956004.581.13.camel@gaston>
References: <1060956004.581.13.camel@gaston>
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Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
>
> Currently, when enabling slab debugging, we lose the property of
> having the objects aligned on a cache line size.
> 
> This is, imho, an error, especially if GFP_DMA is passed. Such an
> object _must_ be cache alined (and it's size rounded to a multiple
> of the cache line size).

Well the theory is that SLAB_HWCACHE_ALIGN is advisory and
SLAB_MUST_HWCACHE_ALIGN is compulsory.

You're looking for compulsory alignment on the generic kmalloc() slab
pools, so we're a bit screwed.

I guess the redzoning would need to be taught to always pad by a full
cacheline.

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